26,811 research outputs found
Whole-body averaged specific absorption rate estimation using a personal, distributed exposimeter
For the first time, a body area network (BAN) is used to construct a personal, distributed exposimeter (PDE), which can measure the whole-body averaged specific absorption rate (SAR(wb)) in real life, together with the incident power density (S-inc). The BAN consists of four textile antennas with integrated radio frequency receiver nodes tuned to the Global System for Mobile Communications (GSM) 900 downlink band. Calibration measurements at 942.5 MHz, using a human subject, are performed in an anechoic chamber. These are combined with numerical simulations to estimate both SAR(wb) and S-inc from the averaged received power on the PDE. The PDE has 50% prediction intervals of 3 dB on S-inc and 3.3 dB on the SAR(wb), caused by the presence of the human body, whereas the best single textile antenna in our measurements exhibits PI50's of 7.1 dB on S-inc and 5 dB on SAR(wb). Measurements using the PDE are carried out in Ghent, Belgium, during which a median S-inc = 47 mu W/m(2) and SAR(wb) = 0.25 mu W/kg are measured
Calibration of the LOFAR low-band antennas using the Galaxy and a model of the signal chain
The LOw-Frequency ARray (LOFAR) is used to make precise measurements of radio
emission from extensive air showers, yielding information about the primary
cosmic ray. Interpreting the measured data requires an absolute and
frequency-dependent calibration of the LOFAR system response. This is
particularly important for spectral analyses, because the shape of the detected
signal holds information about the shower development. We revisit the
calibration of the LOFAR antennas in the range of 30 - 80 MHz. Using the
Galactic emission and a detailed model of the LOFAR signal chain, we find an
improved calibration that provides an absolute energy scale and allows for the
study of frequency-dependent features in measured signals. With the new
calibration, systematic uncertainties of 13% are reached, and comparisons of
the spectral shape of calibrated data with simulations show promising
agreement.Comment: 23 pages, 10 figure
Technical design and commissioning of the KATRIN large-volume air coil system
The KATRIN experiment is a next-generation direct neutrino mass experiment
with a sensitivity of 0.2 eV (90% C.L.) to the effective mass of the electron
neutrino. It measures the tritium -decay spectrum close to its endpoint
with a spectrometer based on the MAC-E filter technique. The -decay
electrons are guided by a magnetic field that operates in the mT range in the
central spectrometer volume; it is fine-tuned by a large-volume air coil system
surrounding the spectrometer vessel. The purpose of the system is to provide
optimal transmission properties for signal electrons and to achieve efficient
magnetic shielding against background. In this paper we describe the technical
design of the air coil system, including its mechanical and electrical
properties. We outline the importance of its versatile operation modes in
background investigation and suppression techniques. We compare magnetic field
measurements in the inner spectrometer volume during system commissioning with
corresponding simulations, which allows to verify the system's functionality in
fine-tuning the magnetic field configuration. This is of major importance for a
successful neutrino mass measurement at KATRIN.Comment: 32 pages, 16 figure
Determination of Electromagnetic Fields and Tritium Column Density for Neutrino Mass Analysis with KATRIN
Das KArlsruher TRitium Neutrino (KATRIN) Experiment hat als Ziel die effektive Elektron-Antineutrinomasse modellunabhängig mit einer Sensitivität von 0.2 eV (90 % C.L.) zu bestimmen, indem das Tritium -Zerfallspektrum nahe dem kinematischen Endpunkt untersucht wird. Um dieses Ziel zu erreichen ist eine genaue Charakterisierung der KATRIN Antwortfunktion für Signalelektronen erforderlich. In der vorliegenden Arbeit werden zwei wichtige Komponenten der Antwortfunktion mit großer Genauigkeit untersucht, nämlich die elektromagnetischen Felder im KATRIN Aufbau sowie die Gasmenge in der Tritiumquelle
Dosimetric evidence confirms computational model for magnetic field induced dose distortions of therapeutic proton beams
Given the sensitivity of proton therapy to anatomical variations, this cancer
treatment modality is expected to benefit greatly from integration with
magnetic resonance (MR) imaging. One of the obstacles hindering such an
integration are strong magnetic field induced dose distortions. These have been
predicted in simulation studies, but no experimental validation has been
performed so far. Here we show the first measurement of planar distributions of
dose deposited by therapeutic proton pencil beams traversing a one-Tesla
transversal magnetic field while depositing energy in a tissue-like phantom
using film dosimetry. The lateral beam deflection ranges from one millimeter to
one centimeter for 80 to 180 MeV beams. Simulated and measured deflection agree
within one millimeter for all studied energies. These results proof that the
magnetic field induced proton beam deflection is both measurable and accurately
predictable. This demonstrates the feasibility of accurate dose measurement and
hence validates dose predictions for the framework of MR-integrated proton
therapy
The IceCube Neutrino Observatory - Contributions to ICRC 2015 Part II: Atmospheric and Astrophysical Diffuse Neutrino Searches of All Flavors
Papers on atmospheric and astrophysical diffuse neutrino searches of all
flavors submitted to the 34th International Cosmic Ray Conference (ICRC 2015,
The Hague) by the IceCube Collaboration.Comment: 66 pages, 36 figures, Papers submitted to the 34th International
Cosmic Ray Conference, The Hague 2015, v2 has a corrected author lis
The Atacama Cosmology Telescope: Data Characterization and Map Making
We present a description of the data reduction and mapmaking pipeline used
for the 2008 observing season of the Atacama Cosmology Telescope (ACT). The
data presented here at 148 GHz represent 12% of the 90 TB collected by ACT from
2007 to 2010. In 2008 we observed for 136 days, producing a total of 1423 hours
of data (11 TB for the 148 GHz band only), with a daily average of 10.5 hours
of observation. From these, 1085 hours were devoted to a 850 deg^2 stripe (11.2
hours by 9.1 deg) centered on a declination of -52.7 deg, while 175 hours were
devoted to a 280 deg^2 stripe (4.5 hours by 4.8 deg) centered at the celestial
equator. We discuss sources of statistical and systematic noise, calibration,
telescope pointing, and data selection. Out of 1260 survey hours and 1024
detectors per array, 816 hours and 593 effective detectors remain after data
selection for this frequency band, yielding a 38% survey efficiency. The total
sensitivity in 2008, determined from the noise level between 5 Hz and 20 Hz in
the time-ordered data stream (TOD), is 32 micro-Kelvin sqrt{s} in CMB units.
Atmospheric brightness fluctuations constitute the main contaminant in the data
and dominate the detector noise covariance at low frequencies in the TOD. The
maps were made by solving the least-squares problem using the Preconditioned
Conjugate Gradient method, incorporating the details of the detector and noise
correlations. Cross-correlation with WMAP sky maps, as well as analysis from
simulations, reveal that our maps are unbiased at multipoles ell > 300. This
paper accompanies the public release of the 148 GHz southern stripe maps from
2008. The techniques described here will be applied to future maps and data
releases.Comment: 20 pages, 18 figures, 6 tables, an ACT Collaboration pape
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